PE-CycleGAN network based CBCT-sCT generation for nasopharyngeal carsinoma adaptive radiotherapy

doi:10.12122/j.issn.1673-4254.2025.01.21

Abstract

Abstract:

Objective To explore the synthesis of high-quality CT (sCT) from cone-beam CT (CBCT) using PE-CycleGAN for adaptive radiotherapy (ART) for nasopharyngeal carcinoma. Methods A perception-enhanced CycleGAN model "PE-CycleGAN" was proposed, introducing dual-contrast discriminator loss, multi-perceptual generator loss, and improved U-Net structure. CBCT and CT data from 80 nasopharyngeal carcinoma patients were used as the training set, with 7 cases as the test set. By quantifying the mean absolute error (MAE), peak signal-to-noise ratio (PSNR), structural similarity index (SSIM), as well as the dose gamma pass rate and the relative dose deviations of the target area and organs at risk (OAR) between sCT and reference CT, the image quality and dose calculation accuracy of sCT were evaluated. Results The MAE of sCT generated by PE-CycleGAN compared to the reference CT was (56.89±13.84) HU, approximately 30% lower than CBCT's (81.06±15.86) HU (P<0.001). PE-CycleGAN's PSNR and SSIM were 26.69±2.41dB and 0.92±0.02 respectively, significantly higher than CBCT's 21.54±2.37dB and 0.86±0.05 (P<0.001), indicating substantial improvements in image quality and structural similarity. In gamma analysis, under the 2 mm/2% criterion, PE-CycleGAN's sCT achieved a pass rate of (90.13±3.75)%, significantly higher than CBCT's (81.65±3.92)% (P<0.001) and CycleGAN's (87.69±3.50)% (P<0.05). Under the 3 mm/3% criterion, PE-CycleGAN's sCT pass rate of (90.13±3.75)% was also significantly superior to CBCT's (86.92±3.51)% (P<0.001) and CycleGAN's (94.58±2.23)% (P<0.01). The mean relative dose deviation of the target area and OAR between sCT and planned CT was within ±3% for all regions, except for the Lens Dmax (Gy), which had a deviation of 3.38% (P=0.09). The mean relative dose deviations for PTVnx HI, PTVnd HI, PTVnd CI, PTV1 HI, PRV_SC, PRV_BS, Parotid, Larynx, Oral, Mandible, and PRV_ON were all less than ±1% (P>0.05). Conclusion PE-CycleGAN demonstrates the ability to rapidly synthesize high-quality sCT from CBCT, offering a promising approach for CBCT-guided adaptive radiotherapy in nasopharyngeal carcinoma.

Key words: cone-beam CT, synthetic CT images, adaptive radiotherapy, deep learning, generative adversarial network

Yadi HE, Xuanru ZHOU, Jinhui JIN, Ting SONG. PE-CycleGAN network based CBCT-sCT generation for nasopharyngeal carsinoma adaptive radiotherapy[J]. Journal of Southern Medical University, 2025, 45(1): 179-186.

Figures/Tables 8

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Method	2 mm/2%	3 mm/3%	P value (vs CBCT)	P value (vs CycleGan)
CBCT	(81.65±3.92) %	(86.92±3.51) %	-	-
CycleGAN	(87.69±3.50) %	(94.58±2.23) %	-	-
PE-CycleGAN	(90.13±3.75) %	(97.20±2.52) %	<0.001 (2 mm/2%), <0.001 (3 mm/3%)	<0.05 (2 mm/2%), <0.01 (3 mm/3%)

Method	2 mm/2%	3 mm/3%	P value (vs CBCT)	P value (vs CycleGan)
CBCT	(81.65±3.92) %	(86.92±3.51) %	-	-
CycleGAN	(87.69±3.50) %	(94.58±2.23) %	-	-
PE-CycleGAN	(90.13±3.75) %	(97.20±2.52) %	<0.001 (2 mm/2%), <0.001 (3 mm/3%)	<0.05 (2 mm/2%), <0.01 (3 mm/3%)

Structure	Parameter	CT	sCT	Relative deviation (%)	P
PTVnx	HI	1.07±0.02	1.08±0.03	0.93±0.93	0.28
	CI	0.58±0.13	0.59±0.12	1.72±1.72	0.36
PTVnd	HI	1.11±0.07	1.11±0.06	0.00±0.90	0.95
	CI	0.13±0.10	0.13±0.10	0.00±0.00	1.00
PTV1	HI	1.17±0.03	1.17±0.03	0.00±0.85	0.89
	CI	0.46±0.14	0.47±0.14	2.17±2.17	0.42
PTV2	HI	1.41±0.09	1.39±0.06	-1.42±1.42	0.18
	CI	0.68±0.14	0.69±0.13	1.47±1.47	0.33
PRV_SC	D_max (Gy)	45.59±5.13	45.51±4.84	-0.17±0.17	0.82
	D_mean (Gy)	36.10±4.14	35.98±3.97	-0.33±0.33	0.65
PRV_BS	D_max (Gy)	61.91±7.33	62.03±7.38	0.19±0.19	0.78
	D_mean (Gy)	27.55±7.20	27.73±7.38	0.65±0.65	0.52
Parotid	V₃₀ (%)	49.91±8.82	49.41±8.64	-1.00±1.00	0.31
	D_mean (Gy)	33.67±3.83	33.55±3.89	-0.36±0.36	0.64
Temp	D_max (Gy)	67.04±9.74	67.92±9.98	1.31±1.31	0.22
	D_mean (Gy)	11.16±7.90	11.41±8.03	2.24±2.24	0.14
Larynx	D_mean (Gy)	41.78±6.56	41.72±7.06	-0.14±0.14	0.87
Oral	D_mean (Gy)	36.20±5.51	36.20±5.70	0.00±0.00	1.00
Mandible	D_max (Gy)	63.50±7.06	63.66±6.97	0.25±0.25	0.73
	D_mean (Gy)	35.59±6.73	35.53±6.65	-0.17±0.17	0.82
Lens	D_max (Gy)	3.55±2.47	3.67±2.51	3.38±3.38	0.09
	D_mean (Gy)	5.81±4.07	5.84±4.08	0.52±0.52	0.67
Eye	D_max (Gy)	24.95±27.58	25.28±27.22	1.32±1.32	0.25
PRV_ON	D_mean (Gy)	18.90±2.95	18.87±2.90	-0.16±0.16	0.84

Structure	Parameter	CT	sCT	Relative deviation (%)	P
PTVnx	HI	1.07±0.02	1.08±0.03	0.93±0.93	0.28
	CI	0.58±0.13	0.59±0.12	1.72±1.72	0.36
PTVnd	HI	1.11±0.07	1.11±0.06	0.00±0.90	0.95
	CI	0.13±0.10	0.13±0.10	0.00±0.00	1.00
PTV1	HI	1.17±0.03	1.17±0.03	0.00±0.85	0.89
	CI	0.46±0.14	0.47±0.14	2.17±2.17	0.42
PTV2	HI	1.41±0.09	1.39±0.06	-1.42±1.42	0.18
	CI	0.68±0.14	0.69±0.13	1.47±1.47	0.33
PRV_SC	D_max (Gy)	45.59±5.13	45.51±4.84	-0.17±0.17	0.82
	D_mean (Gy)	36.10±4.14	35.98±3.97	-0.33±0.33	0.65
PRV_BS	D_max (Gy)	61.91±7.33	62.03±7.38	0.19±0.19	0.78
	D_mean (Gy)	27.55±7.20	27.73±7.38	0.65±0.65	0.52
Parotid	V₃₀ (%)	49.91±8.82	49.41±8.64	-1.00±1.00	0.31
	D_mean (Gy)	33.67±3.83	33.55±3.89	-0.36±0.36	0.64
Temp	D_max (Gy)	67.04±9.74	67.92±9.98	1.31±1.31	0.22
	D_mean (Gy)	11.16±7.90	11.41±8.03	2.24±2.24	0.14
Larynx	D_mean (Gy)	41.78±6.56	41.72±7.06	-0.14±0.14	0.87
Oral	D_mean (Gy)	36.20±5.51	36.20±5.70	0.00±0.00	1.00
Mandible	D_max (Gy)	63.50±7.06	63.66±6.97	0.25±0.25	0.73
	D_mean (Gy)	35.59±6.73	35.53±6.65	-0.17±0.17	0.82
Lens	D_max (Gy)	3.55±2.47	3.67±2.51	3.38±3.38	0.09
	D_mean (Gy)	5.81±4.07	5.84±4.08	0.52±0.52	0.67
Eye	D_max (Gy)	24.95±27.58	25.28±27.22	1.32±1.32	0.25
PRV_ON	D_mean (Gy)	18.90±2.95	18.87±2.90	-0.16±0.16	0.84

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